1. Field of the Invention
The present invention relates to a pressure vessel wherein the gasification of fuel, residual and waste materials can be carried out in an entrained-bed type gasification reaction.
2. Description of the Related Art
Fuel, residual and waste materials are to be understood as meaning those with or without an ash content, such as brown or hard coals and their cokes, water/coal suspensions, but also oils, tars and slurries, as well as residues or wastes from chemical and wood pulping processes from the papermaking and pulp industry, such as for example black liquor from the Kraft process, as well as solid and liquid fractions from the waste management and recycling industry, such as used oils, PCB-containing oils, plastic and domestic refuse fractions or their processing products, and residual and waste materials from the chemical industry, such as for example nitrogen- and halogen-containing hydrocarbons or alkali metal salts of organic acids.
The autothermal entrained-bed gasification of solid, liquid and gaseous fuel materials has been known for many years in the field of gas generation. The ratio of fuel material to oxygen-containing gasification agents is selected in such a way that, for reasons of quality of the synthesis gas, higher carbon compounds are cleaved completely to form synthesis-gas components, such as CO and H2, and the inorganic constituents are discharged in the form of molten liquid slag (J. Carl, P. Fritz, NOELL-KONVERSIONSVERFAHREN [NOELL CONVERSION PROCESS], EF-Verlag fxc3xcr Energie- und Umwelttechnik GmbH 1996, p. 33 and p. 73).
Using various systems which have gained acceptance in the prior art, gasification gas and the molten liquid inorganic fraction, e.g. slag, can be discharged from the reaction chamber of the gasification appliance separately or together (DE 19718131.7).
Both systems which are provided with a refractory lining and cooled systems have been introduced for internally delimiting the contour of the reaction chamber of the gasification system (DE 4446803 A1).
Gasification systems which are provided with a refractory lining have the advantage of low heat losses and therefore offer an energy-efficient conversion of the fuel materials supplied. However, they can only be used for ash-free fuel materials, since the liquid slag which flows off the inner surface of the reaction chamber during the entrained-bed gasification dissolves the refractory lining and therefore only allows very limited operating times to be achieved before an expensive refit is required.
In order to eliminate this drawback which is encountered with ash-containing fuel materials, cooled systems working on the principle of a diaphragm wall have therefore been provided. The cooling initially results in the formation of a solid layer of slag on the surface facing the reaction chamber, the thickness of which layer increases until the further slag ejected from the gasification chamber runs down this wall in liquid form and flows out of the reaction chamber, for example together with the gasification gas. Such systems are extremely robust and guarantee long operating times. A significant drawback of such systems consists in the fact that up to approx. 5% of the energy introduced is transferred to the cooled screen.
Various fuel and waste materials, such as for example heavy-metal- or light-ash-containing oils, tars or tar-oil solid slurries contain too little ash to form a sufficiently protective layer of slag with cooled reactor walls, resulting in additional energy losses, yet on the other hand the ash content is too high to prevent the refractory layer from melting away or being dissolved if reactors with a refractory lining were to be used and to allow sufficiently long operating times to be achieved before a refit is required.
A further drawback is the complicated structure of the reactor wall, which may lead to considerable problems during production and in operation. For example, the reactor wall of the entrained-bed gasifier shown in J. Carl, P. Fritz: NOELL-KONVERSIONSVERFAHREN [NOELL CONVERSION PROCESS], EF-Verlag fxc3xcr Energie- und Umwelttechnik GmbH, Berlin 1996, p. 33 and p. 73 comprises an unpressurized water shell, the pressure shell, which is protected against corrosion inside with a tar/epoxy resin mixture and is lined with lightweight refractory concrete, and the cooling screen which, in the same way as a diaphragm wall which is conventionally used in the construction of boilers, comprises cooling tubes which are welded together in a gas tight manner, through which water flows, which are pinned and which are lined with a thin layer of SiC. Between the cooling screen and the pressure shell, which is lined with refractory concrete, there is a cooling-screen gap which has to be purged with a dry oxygen-free gas in order to avoid backflows and condensate formation.
To eliminate the above drawbacks, DE 198 29 385 C1 has disclosed an appliance in which a cooling gap was arranged inside the pressure shell of the gasification reactor, which gap is delimited by a cooled wall provided with ceramic material or a layer of slag in the direction toward the reaction chamber. This appliance has the advantage of representing a simple technical solution with regard to the reactor design. The drawback is that only limited pressure differences between the reaction chamber and the cooling gap are possible, leading to a considerable outlay on control and safety engineering. For example, in the event of pressure fluctuations in the reaction chamber or during start-up and run-down processes, the pressure in the cooling gap has to be constantly adapted to the pressure in the reaction chamber. This may cause problems in the event of rapid depressurization of the reaction chamber for safety engineering reasons, since the pressure in the cooling gap cannot be adapted as quickly, and this may lead to mechanical destruction of the cooling shell. DD 226 588 A1 has disclosed a pinned screen for heating installations in which the pins are designed as spacers between pressure shell or pressure shell and inner skin. However, this screen cannot be used to good effect if the ash contents in the fuel and waste materials differ.
Working on the basis of this prior art, the object of the invention is to provide an appliance which, while being simple and reliable to operate, is able to cope with a very wide range of ash contents in the fuel and waste materials and in which the pressure in the cooling gap or cooling system does not have to be constantly adapted to the pressure in the reaction chamber.
Another object of the invention is to provide a gasification reactor vessel with a cooling system for cooling the reactor vessel and an inwardly adjacent protective refractory layer with coolant supplied at a higher pressure than a pressure in the gasification chamber without imposing an undesirable or potentially damaging force of the coolant pressure on the refractory layer. A method for cooling the refractory layer and reactor vessel also provided.
The gasification reactor vessel for the gasification of carbon-containing fuel, residual and waste materials using an oxygen-containing oxidizing agent and in a gasification chamber which is designed as an entrained-bed reactor, at pressures between ambient pressure and 80 bar, preferably between ambient pressure and 30 bar, in which the contour of the reaction chamber is delimited by a cooling system, and the pressure in the cooling system is always at a higher level than the pressure in the reaction chamber, is distinguished by the fact that the cooling channels are formed by webs which are in contact both with a refractory protective layer and with a pressure shell.
As a result, the cooling system withstands and is unaffected by the maximum possible pressure difference that can exist between the reaction chamber and atmospheric pressure.
The cross section of the cooling channels is selected in such a way that pressure fluctuations in the reaction chamber can be absorbed without having to readjust the cooling system. The cross section of the cooling channels may be semicircular, oval or polygonal. The exemplary embodiment has semicircular channels.
The appliance is also distinguished by the fact that, from the outside inward, its structure is as follows: pressure shell, cooling channels, refractory protective layer and caked slag or refractory lining.
An advantage of the invention is that the pressure and temperature in the cooling channels can be selected in such a way that the cooling channels are operated above or below the coolant boiling point.
Depending on the operating conditions, the materials used for the cooling channels may be heat-resistant carbon steels (e.g. 16 Mo3) or corrosion-resistant steels.
Furthermore, it is advantageous for the cooling channels to comprise webs which are welded onto the pressure shell and are closed off by semicircular or arced segments.
Furthermore, it is essential to the invention that the refractory protective layer be attached by spread wall ties or pin-like wall ties which are welded onto the semicircular or arced segments.
The appliance according to the invention is suitable for the gasification of fuel, waste and residual materials with a very wide range of ash contents, and for the combined gasification of hydrocarbon-containing gases, liquids and solids.
According to the invention, the contour of the reaction chamber for the gasification process is delimited by a refractory lining or by a layer of solidified slag. If the reaction chamber is lined with refractory material, intensive cooling protects this material or causes liquid slag to solidify, so that a thermally insulating layer is formed. The cooling is provided by water-cooled cooling channels, it being possible to set operating conditions above or below the boiling point.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.